The urban cortex

A talk given at Lombardini22 architects in Milan on 13th May 2025.

The idea I’d like to explore this evening is that cities serve a higher purpose than we typically credit them with, and this idea is that cities are natural extensions of the human brain. Far from being artificial, alien objects, cities work with us, their users, to help us solve the problems of our times. Cities are extensions of our brains and, just like our brains, cities are sophisticated computers.

At least they are, if we design them well. 

Great cities are not just beautiful to look at and stimulating to be in. They are also highly efficient human transactions machines: bringing people together to form relationships and generate outcomes. Cities are the outermost layer of our common existence. Hence the title of this talk: the ‘urban cortex’.  

One challenge when discussing cities is that urban commentators often begin by describing cities as chaotic, that their street networks are ‘labyrinthine’. This is a lazy approach to urbanism – and not one that we share at Space Syntax. Instead, we’ve spent the last 50 years studying the apparent chaos of cities and discovering regularities within them – of spatial layout, of land use distribution, of density, mobility and the distribution of inequalities. 

These discoveries help us both to understand cities and to better design them. 

Cities are not chaotic. We don’t build them by chance. Within their apparently labyrinthine randomness there are structures that organise the ways we move through cities – and interact with each other within them.

There are regularities that allow us to understand cities – not just as urban scientists might pick them apart but as every day users make sense of the places they’re in:

• how they feel comfortable in them
• feel like they want to visit and explore them
• meet people in them
• go to work in them
• invest their time and their money 
• have fun
• feel excitement. 

This is the ‘urban buzz’ that draws people to cities.  

Cities are sensory stimulators. They are invigorators, enhancers and accelerators of the human condition. And, generally, of a collective human condition that brings people together rather than keeps us apart, a condition that forms social bonds and shared cultures. 

But of course, there are also moments when cities don’t work for us:

• when we feel scared within them
• when we feel uncomfortable
• when things go wrong
• when we get lost
• when there are accidents, injuries and deaths, whether accidental or deliberate.

Cities are places that attract passions, protests, acts of violence and terror. 

Cities are places that work for each of us and each of us have our own unique personalities informed by unique experiences. No one person is quite like anyone else. 

Or are we?

It turns out that there are similarities in the way we use cities that underpin our collective and individual experience of them. 

Here’s a simple experiment that asks a straightforward question: which is the easiest route between A and B?

Would we take the shortest route, that wriggles its way through the back streets of the city? Many architects, including me, were taught that people like to do this – we were told that these wriggling routes create surprise around every corner, and that people love to be surprised.

Or would we choose a slightly longer route but with fewer twists and turns?

Or would we select some other permutation of streets?

We don’t have to guess. We can go out and count. Or set up a camera and collect data…

Watching other people navigate through space is a fascinating education. Here’s a first lesson: people try to cut corners wherever they can. You might just be able to make out the curving metal edge of the path, and can you see how the grass has been worn away just inside each of the curves?

This person is taking it to an extreme. As we follow them walking along the path we can see that they have other things on their mind. This is an important lesson: people aren’t just thinking about moving – they’re thinking about other things as well. We’ll come back to this lesson shortly.

Here’s another lesson: when the sightline is blocked, you see fewer people moving…

…whereas when there’s a glimpse into the distance you see more people taking that route.

And when the sightline is long and unfolding, you find the greatest volumes of people.

Systematic observations allow us to create movement maps that record people’s individual preferences.

And by doing so, we’ve discovered that:

• most people most of the time take the shortest and most direct route between origin and destination (people are predictable!)
• on most streets of cities, most of the people in them will be moving rather than standing or sitting still
• most of this movement will be passing through the street rather than starting or ending a journey on it (streets are full of strangers!).

And when it comes to the physical form of cities, it may seem that no one city is quite like any other, yet:

• most streets in cities are relatively short and connect only with a small number of other streets (this is also where most people live in cities)
• only a few streets will be of any significant length (and in these will be located most of the shops and offices)
• street networks at the centres of cities will be grids (not necessarily rectilinear grids but networks where if you turn left, left and left again you end up back at where you started)
• there will be a greater density of routes (more ‘permeability’) at the centres of cities (where there are more shops and offices) than at the edges (where more people live)
• buildings will be taller in the centres than at the edges
• most buildings will touch other buildings rather than start apart from them (it’s how we get streets: the basic building blocks of the urban DNA) (just like most trees in nature touch other trees…)

Until Ebenezer Howard and Le Corbusier turned these rules upside down. 

And we taught planners to separate where we live from where we work, from where we shop, from where we take entertainment.

And we taught architects to only design object buildings. 

And we taught highways engineers to design roads to drive people at speed between one zone and another (except they seem to end up creating traffic jams rather than fast highways). 

And people living and working in car-dependent places are increasingly obese, lonely and angry. 

These cities are carboniferous (transport emissions can be 60% of the total carbon footprint). They’ve fuelled the climate emergency. 

In our work at Space Syntax we think about the ‘good city’ in order to create more of it. We start with the premise that, first and foremost, cities are social objects, created by humans, for humans.

And we then try to objectively define them, starting with the public space between buildings.

In terms of mobility, this means that we focus on walking, cycling and public transport since these are the healthiest, least carbon-intensive forms of movement. 

But, in doing so, our mind is not only on the mechanics of mobility but, even more importantly, on its ultimate purpose, which is typically some form of social or economic transaction. 

For this reason we should think of cities not only as ‘mobility machines’ but as ‘transaction machines’. 

And this means that every opportunity should be taken to design cities for transaction. Of course the obvious ‘transaction places’ are in parks and public spaces, as well as in offices (like this) and around dining tables, whether in restaurants or at home. 

But the often-overlooked fifth category of transaction is the street itself. 

One of the most damaging outcomes of urban planning over the last century has been to strip streets of their function as transactions environments. 

Much of our work at Space Syntax is attempting to restore this function:

• by reducing the speed limit on the streets to make them safer places to be in
• creating planning and architectural design codes that activate the ground floor frontages of buildings so that they address streets with shops, cafés and restaurants
• providing benches for public use
• designing landscape strategies that shade streets to improve environmental comfort. 

Our work aims to restore the essential purpose of cities, which is to help us solve the problems of our times, whether these are societal, economic or environmental. Good cities do this by bringing people together to form relationships that generate new knowledge, new technologies and new ways of living.

We can think of cities as powerful computers. Not unlike the human brain, cities generate phenomena in the form of new experiences that stimulate the ways that people think and act.

In doing so, cities are, I believe, natural extensions of our brains: the outer layer, or cortex, of the human body. In recognising this unique and precious property of good cities we can bring renewed purpose to the making and remaking of good cities.